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Welcome to InkscapeForum, Megan!
That black rectangle is the image border. It's not actually part of the image. Depending on how you will use your image, it might be important that all of your image falls inside the border. But it can be removed, if you want.
So since that's not part of the image, you actually have a blank page there! You will need to draw some kind of border to contain your Fill. You could do that with the Rectangle tool
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or Pen tool
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. Then the best way to apply color would be with a Fill, by either clicking on a color in the palette, or using the Object menu > Fill and Stroke (or button on the Command bar (
http://tavmjong.free.fr/INKSCAPE/MANUAL ... atomy.html).
Or, if the reason you want color inside the image border, is to create a background color, there is another option. File menu > Document Properties > Page tab > General > Background. Click the bar that has a checkerboard pattern, and you can change the background color and/or transparency there. Of course, as you will see, it applies color to the whole canvas, not just inside the border.
I'm not sure whether changing the background color, or drawing a rectangle would be your best option. But you will know, according to your plans for the image.
I hope that helps. Also just to let you know, I'll be moving your topic to the Help forum (where most help topics are posted)
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